Influencer Ayolyi thought she was 'bone-thin' — but her body fat told a different story

Model and influencer Ayolyi has revealed that she once had high body fat and low muscle mass despite not being overweight — a condition commonly known as "skinny fat."

In a video recently posted to Ayolyi's YouTube channel, her boyfriend Kim Hyeong-bae, a traditional Korean medicine doctor, recalled the first time she visited his clinic. "She didn't look like she needed to lose any weight at all," he said.

She appeared slim on the outside, but a body composition test told a different story. "Her body fat percentage was quite high and her muscle mass was low," Kim said. "It was a classic skinny-fat type."

Skinny fat is not an official medical diagnosis with a single standardized definition. The term is generally used to describe people whose body mass index falls within the normal range but who carry a relatively high proportion of body fat and insufficient muscle. The medical community has increasingly categorized this as "normal weight obesity" and is researching its links to metabolic health. A study published in 2025 found that people with a normal BMI but excess body fat may face elevated risks of insulin resistance and cardiovascular and metabolic disease.

Normal weight, high body fat — what BMI misses

BMI is calculated by dividing a person's weight by the square of their height. It is easy to compute and widely used to assess obesity risk, but it cannot distinguish whether weight comes from fat or muscle.

Two people of the same height and weight can have vastly different body compositions — one who exercises consistently and has built up muscle, and another who is largely sedentary and carries a higher proportion of body fat.

That is why someone who looks slim, like Ayolyi, can still show low muscle mass and a relatively high body fat percentage on a body composition test.

Crash dieting — repeatedly cutting food intake drastically without adequate strength training — can cause muscle loss alongside weight loss. When weight returns, fat tends to account for a larger share, meaning body fat percentage can climb even at a similar overall weight.

A sedentary lifestyle compounds the problem. Spending most of the day sitting without dedicated exercise can reduce muscle mass and increase body fat even without significant weight change. A diet low in protein and heavy in refined carbohydrates — bread, noodles and snacks — makes managing body composition even harder.

Body fat percentage and muscle mass readings from a body composition analyzer can serve as useful reference points for understanding one's physical condition. Results can vary depending on hydration, recent meals and exercise, however, so tracking changes over time under consistent conditions is more informative than any single measurement.

Slim but carrying belly fat — effects on blood sugar and blood pressure

With skinny fat, what matters more than the number on the scale is where fat has accumulated and how much.

Visceral fat — the fat that builds up around internal organs in the abdominal cavity — is more closely linked to metabolic disease than subcutaneous fat stored just beneath the skin. As visceral fat increases, insulin function can decline and levels of blood triglycerides, blood sugar and blood pressure may all be affected.

Studies analyzing normal weight obesity have found that people in this category tend to show worse markers for metabolic syndrome, hypertension, diabetes and dyslipidemia than people with the same BMI but normal body fat levels.

Waist circumference, measured alongside weight, can help identify abdominal fat. In South Korea, the threshold for abdominal obesity is a waist of 90 centimeters or more for adult men and 85 centimeters or more for women. Even with a normal BMI, exceeding these measurements signals a need to address abdominal fat.

For someone with slim limbs and a normal weight but a noticeably protruding abdomen, the focus should not be solely on losing more weight. Checking waist circumference, body fat and muscle mass together gives a more complete picture.

Low muscle mass itself is also a significant concern. Muscles do more than enable movement — they are a primary tissue for glucose uptake. Maintaining adequate muscle mass helps prevent the decline in strength that comes with aging and supports long-term metabolic health.

Build muscle, not just lose weight — combine cardio and strength training

Simply trying to lose more weight is not necessarily the right approach for addressing skinny fat.

For someone already at a normal weight, cutting food intake too aggressively can reduce muscle as well as fat. The result can be a drop in weight without a meaningful reduction in body fat percentage.

The goal should not be to push the number on the scale as low as possible, but to reduce body fat while maintaining or increasing muscle mass.

On the dietary side, cutting out carbohydrates entirely is not necessary. A better approach is to include fiber-rich foods such as brown rice, mixed grains and whole grains in appropriate amounts while making sure each meal contains protein. Good protein sources include meat, fish, eggs, tofu, legumes and dairy products, ideally eaten alongside vegetables and fruit. Sugary beverages, snacks and desserts should be consumed less frequently.

For exercise, combining aerobic activity — walking, running or cycling — with strength training is most effective. Consistently performing compound movements that engage large muscle groups, such as squats, lunges and deadlifts, helps maintain lower-body and core muscle mass.

The WHO recommends that adults get 150 to 300 minutes of moderate-intensity aerobic activity per week, or 75 to 150 minutes of vigorous activity. It also advises muscle-strengthening exercises targeting major muscle groups on at least two days per week.

Starting at high intensity is not necessary. For those who have not been exercising regularly, a good approach is to gradually increase daily walking and begin with light strength training two to three times a week, slowly adding weight and repetitions over time.

Even in someone who looks perfectly slim, like Ayolyi, an imbalance between body fat and muscle mass can exist beneath the surface. It is a reminder of why weight and BMI alone are not enough to assess overall physical condition.

In managing one's body, changing body composition matters more than chasing a lower number on the scale. For those already at a normal weight, adjusting diet and exercise habits to reduce abdominal fat and preserve muscle — rather than pursuing aggressive weight loss — is a healthier path to long-term body management.